Participación de las mitocondrias en la respuesta de defensa de Arabidopsis thaliana frente a la infección de microorganismos patógenos

  1. Martínez Ayala, Ada
Supervised by:
  1. Carmen Castresana Fernández Director
  2. Yovanny Izquierdo Núñez Director

Defence university: Universidad Autónoma de Madrid

Fecha de defensa: 26 February 2018

Committee:
  1. Pablo Rodríguez Chair
  2. Marta Martín Basanta Secretary
  3. Isabel Allona Alberich Committee member
  4. Monica Pernas Ochoa Committee member
  5. Óscar Lorenzo Sánchez Committee member

Type: Thesis

Abstract

Oxylipins produced by the 9-lipoxygenase pathway act as signaling molecules during the activation of plant defense against pathogen infection. As their receptors and mechanisms of action have not been described, non-responding to oxylipins (noxy) mutants are important tools to identify the cellular components involved in oxylipin signaling and to discover the cellular processes on which they exert their actions. In this work we have selected three mutants, namely noxy5, noxy23 and noxy54, in order to elucidate the participation of NOXY proteins in defense activation against the infection by hemibiotrophic and necrotrophic pathogens such as the bacteria Pseudomonas syringae, and the fungus Alternaria brassicicola. Map-based cloning followed by whole genome sequencing of these mutants showed that, in all three cases, the affected genes encode mitochondrial proteins associated with the translation of messengers in this organelle. Thus, the noxy5 mutation was located at the At3g02010 locus, which encodes a PPR protein (PENTATRICOPEPTIDE REPEAT CONTAINING protein); noxy23 was located at the At1g64880 locus encoding a S5 ribosomal protein; whereas noxy54 affects the At1g55870 locus encoding a poly-A specific exoribonuclease. Characterization of noxy5, noxy23 and noxy54 shows the formation of mitochondrial accumulations, as well as altered responses to mitochondrial damage, in comparison with wild type plants. This indicates that NOXY proteins regulate mitochondrial function in both basal and stress conditions. Analysis of noxy defense responses revealed important alterations regarding symptom formation, pathogen growth and induction of genes from several defense pathways. Results obtained in these studies showed the increased susceptibility of noxy5, noxy23 and noxy54 plants to the two classes of pathogens examined, and allow to define the action of the corresponding NOXY proteins as positive regulators of defense against both hemibiotrophs and necrotrophs. The fact that the identified genes encode mitochondrial proteins which are directly or indirectly involved in mitochondrial translation is particularly relevant, as it points to the existence of new plant defense mechanisms dependent on the function of these organelles, which could escape the classical salicylic-jasmonate antagonism.